Photographic emulsion



Patented Dec. 29. 1936 PHOTOGBAPHIC EMULSION Walter Dieterle, Dessau-Ziebigk in Anhalt, Germany, assignor to Agfa Ansco Corporation, Binghamton, N. Y., a corporation of New York No Drawing. Application July 16, 1932, Serial No. 623,017. In Germany July 24, 1931 2- Claims.

My present inventioflzelates to photographic having a tendency for fogging and optically sensitized or hyper-sensitized from fogging while simultaneously stabilizing the same. Another object is these stabilized emulsions themselves.

In U. S. specifications Nos. 1,696,830 and 1,758,577 there is described a method for pro- 1 ducing clear silver halide gelatin emulsions from kinds of gelatin having a tendency to cause fog,

which consists in adding to the emulsion at any stage of its manufacture an organic compound which forinsa silver salt with a solubility in water at 18 C. not surpassing that of silver chloride. The compound may be, for instance; an imidazole, a tetrazole, a thiophene, thioglycollic acid or the like.

This invention is based on the observation that these organic compounds do not only retard the fog-promoting action of certain kinds of gelatin, but are suited to take the place of additions (for instance, potassium' bromide) hitherto used for increasing the stability of optically sensitized and-particularly hyper-sensitized emulsions. They difier from potassium bromide hitherto-used for this purpose by the advantage that they do not detrimentally aiiect .the sensitization.

.In explanation of the term optically sensi tized, an emulsion is said to be optically sen-.

sitized when, owing to the presencein it of a dyestufi or similar substance having aninherent property of absorbing light, it is rendered sensitive towards regions of the spectrum to which it would otherwise be but little or not at all sensitive.

The compounds areadded to the emulsions which have been hyper-sensitized in known manner, for instance by washing with water or by addition of silver salt solutions, before the emulsions are poured onto thesupport. There 5 may be used a single representative of the said group of substances or amember thereof. The usual known additions may also be incorporated in the emulsion prior to its being poured on the support.-

The following examples illustrate the invention.

Example 1.-To 1 kilo of a panchromatic emulsion ready for being applied to a support and prepared in the usual manner are added 40 cc. of an aqueous solution 011% strength of silver nitrate and 10-20 milligrams of ethylthiotriazole in an alcoholic solution, before the emulsion is poured on the support.

Example 2.-- 0.1 gram of nitrobenzimidazole is added to 1 kilo of a'panchromatic emulsion hyper-sensitized with a. silver nitrate solution according to Example 1, before it is poured on 1 the support.

My invention is not limited to the foregoing examples or to the specific details given therein and I contemplate as included within my invention all such modifications as fall under the scope of the appended claims.

What I claim is:

1. In the manufacture of optically sensitized or hyper-sensitized silver halide emulsions the step which comprises incorporating-insaid emulsion ethylthiotriazoles.

O 2. An optically or hypersensitized-silver halide emulsion containing ethylthiotriazole.

WALTER DIE'I'ERIE. 

